Only the last product got added in the cart

I have a question about the shopping cart capabilities. I am currently testing and put two downloadble audio programs out there. So on my webpage, I have separate "add to cart" and "view cart" buttons for each product. But it appears I can't order more than one download at a time? For example, I clicked add to cart on the first one then it took me to the cart and I pressed continue shopping and added the second product to the cart. But only the second product was in the cart. What's the purpose of a shopping cart if you can only order one product at a time?